Mistake trainer: practise the positions you got wrong

Every Game Review adds your mistakes and blunders to a personal deck. Find the better move, and spaced repetition brings each one back until it sticks.

Updated 29 October 2026 · 2 min read

The fastest way to improve is to stop repeating your own mistakes. The Mistake trainer turns them into personal practice positions — free, with no account needed.

Where the positions come from

Every time you run a Game Review, your mistakes, missed wins and blunders are added to your deck (inaccuracies aren't, so the deck stays focused). After a review you'll see "N mistakes added to your trainer".

Haven't reviewed your recent games? Press Scan my recent games on the trainer page: ChessMess quickly reviews up to 20 of your latest unreviewed games in your browser, with a progress bar and a Cancel button, and adds what it finds.

How practice works

1. The position appears from your side of the board: "Find a better move (you played X)".
2. Play your answer. Stockfish checks it: the best move, a move within about half a pawn of it, or a move that's still clearly winning all count as right.
3. You see the coach's explanation, the best line, and when the card will come back.

Spaced repetition

Cards come back after 1, 3, 7, 14, 30 and 60 days. Get one right and it waits longer; get it wrong (or press Show answer) and it returns tomorrow. Six right answers in a row and a card is mastered. The page shows cards due today, your day streak and how many you've mastered. You can remove any card.

Your deck on every device

As a guest, the deck lives in your browser. With a free account it syncs to your account, so you can practise on your phone what you got wrong on your laptop. The deck holds up to 400 cards; when it's full, the oldest mastered cards make room first.

Rated puzzles

General rated puzzles are still coming soon. Until then, the trainer gives you the most useful puzzles of all: your own.

Questions and answers

Is the mistake trainer free?

Yes, completely, with no limit on reviews or practice. It works without an account; a free account syncs your deck across devices.

Which mistakes are added?

Moves labelled Mistake, Missed win or Blunder in your Game Review. Inaccuracies are left out.